There has been proposed the use of a flexible transparent electrode substrate for electrodes of a liquid crystal display, an electroluminescence display, an electrophotographic recording medium, an electrophoretic recording medium, an electron beam recording medium, a transparent switch, a connector and the like.
The following process have been utilized for the production of such a flexible transparent electrode substrate: A thin film of a metal, such as gold, silver, palladium and the like; or a metal oxide, such as stannum oxide, indium oxide, antimony oxide, cadmium stannum oxide and the like is formed on plastic transparent film by way of a vacuum evaporation process, a sputtering process and a masking layer by a resist ink or a photoresist is formed thereon in the part of desirable electrode pattern. Then, the unnecessary part of the metal thin film or metal oxide thin film is removed by way of a wet or dry etching process, followed by removing the masking layer to obtain a flexible transparent electrode substrate.
However, the transparent electrode substrate obtained by the above process has the following defects.
(1) The abrasion resistance of the substrate is not sufficient, since the metal thin film or metal oxide thin film is weak in surface strength and also a part without forming the metal thin film or metal oxide thin film i.e. a part which the transparent plastic film is exposed is weak in surface strength. PA1 (2) The substrate lacks stability, since the metal thin film or metal oxide thin film is not adhered tightly to the transparent plastic film because the thin film is directly adhered to the transparent plastic film. PA1 (3) Productivity is not good, since it takes quite long time for the drying process when the masking layer is made by a resist ink. PA1 (4) Productivity also is not good, since many steps such as application of photosensitive resin, print and develop of pattern, removal of photoresist and the like is required for making the masking layer by a photoresist. PA1 (5) The electric resistance of the electrode pattern becomes increased or the snapping of the pattern occurs often, since the pattern becomes thin by means of a side-etching when the etching is carried out. PA1 (6) For solving the problem (5), the etching width must be formed when the masking layer is made. It is difficult to control technically the etching width. PA1 (7) The snapping of the electrode pattern easily occurs, since the metal thin film or metal oxide thin film has a stain or damage on the surface when the masking layer is removed. PA1 (8) The cost of the above process is expensive, since the resist ink or photoresist is expensive. PA1 (9) Environmental pollution problems would be associated with a corrosive liquid. PA1 forming, on an insulated transparent substrate film (A), a polymer compound layer (B) formed from at least one class consisting of a polyurethane resin, a polyester resin and an epoxy resin, PA1 forming partly thereon a water-soluble coating layer (C), PA1 further forming thereon a transparent conductive layer (D) having a surface electric resistance of 10 to 10.sup.4 ohm/.quadrature., and PA1 dissolving and removing the water-soluble coating layer (C) and the transparent conductive layer (D) thereon by the aid of washing.
Furthermore, the above process also have the following defects because of the etching process mentioned above. Thus;
Because of the above problems, especially problems (1) and (2), the transparent electrode substrate obtained by the above process can only be used for a limited field or it requires a further treatment, for example by coating it with a protective film in practice. For dissolving the above problems, Japanese patent publication (unexamined) No. 10450/1981 discloses a process in which a hard organic treating layer obtained from a silicon resin, an acrylate resin formed from a compound having acryloyl groups, a vinyl polymer formed from a compound having vinyl groups, etc. is placed between the metal thin film or metal oxide thin film and the transparent plastic film. However, even in this process, it has possibility that the treating layer is affected by an alkali solution or an organic solution used in an etching process. As the result, a material used for the treating layer must be limited to one which is not affected by the alkali solution or the organic solution. Accordingly, there has not been substantially solved the above problems, especially there have been remained the problems associated with the etching process.